関: carboxylate

WordNet

treat (a chemical compound) with carboxyl or carboxylic acid
street name for lysergic acid diethylamide (同)back breaker, battery-acid, dose, dot, Elvis, loony toons, Lucy in the sky with diamonds, pane, superman, window pane, Zen
any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
having the characteristics of an acid; "an acid reaction"
relating to or containing the carboxyl group or carboxyl radical (同)carboxylic
the univalent radical -COOH; present in and characteristic of organic acids (同)carboxyl_group

PrepTutorEJDIC

酸性の / 酸味のある,すっぱい(sour) / (言葉・態度などが)厳しい,しんらつな / 酸 / すっぱいもの / 《俗》=LSD

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/08/17 08:17:58」(JST)

wiki en

[Wiki en表示]

Structure of a carboxylic acid

Carboxylate ion

3D structure of a carboxylic acid

A carboxylic acid /ˌkɑːrbɒkˈsɪlɪk/ is an organic compound that contains a carboxyl group (C(O)OH).^[1] The general formula of a carboxylic acid is R–C(O)OH, with R referring to the rest of the (possibly quite large) molecule. Carboxylic acids occur widely and include the amino acids (which make up proteins) and acetic acid (which is part of vinegar and occurs in metabolism).

Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base forms a carboxylate anion. Carboxylate ions are resonance-stabilized, and this increased stability makes carboxylic acids more acidic than alcohols. Carboxylic acids can be seen as reduced or alkylated forms of the Lewis acid carbon dioxide; under some circumstances they can be decarboxylated to yield carbon dioxide.

1 Example carboxylic acids and nomenclature
2 Carboxyl radical
3 Physical properties
- 3.1 Solubility
- 3.2 Boiling points
- 3.3 Acidity
- 3.4 Odour
4 Characterization
5 Occurrence and applications
6 Synthesis
- 6.1 Industrial routes
- 6.2 Laboratory methods
- 6.3 Less-common reactions
7 Reactions
- 7.1 Specialized reactions
8 See also
9 References
10 External links

Example carboxylic acids and nomenclature

Carboxylic acids are commonly named as indicated in the table below. Although rarely used, IUPAC-recommended names also exist. For example, butyric acid (C₃H₇CO₂H) is, according to IUPAC guidelines, also known as butanoic acid.^[2]

To more easily understand much of the below discussion of reactions involving carboxylic acids it can be helpful to notice that the carboxyl group itself is a "hydroxylated carbonyl group" meaning that two of the carbon atom's four bonds are to an oxygen atom, the carbon atom's third bond is to a second oxygen atom (whose other bond is to a hydrogen atom), and the carbon atom's fourth bond attaches to R. (A carbon atom double bonded to an oxygen atom is a carbonyl group and two of the carbon atom's bonds remain available for bonding. A hydrogen atom bonded to an oxygen atom is a hydroxyl group with the oxygen atom's second bond available for bonding.)

The carboxylate anion R–COO⁻ is usually named with the suffix -ate, so acetic acid, for example, becomes acetate ion. In IUPAC nomenclature, carboxylic acids have an -oic acid suffix (e.g., octadecanoic acid). For trivial names, the suffix is usually -ic acid (e.g., stearic acid).

Straight-chain, saturated carboxylic acids
Carbon atoms	Common name	IUPAC name	Chemical formula	Common location or use
1	Formic acid	Methanoic acid	HCOOH	Insect stings
2	Acetic acid	Ethanoic acid	CH₃COOH	Vinegar
3	Propionic acid	Propanoic acid	CH₃CH₂COOH	Preservative for stored grains
4	Butyric acid	Butanoic acid	CH₃(CH₂)₂COOH	Butter
5	Valeric acid	Pentanoic acid	CH₃(CH₂)₃COOH	Valerian
6	Caproic acid	Hexanoic acid	CH₃(CH₂)₄COOH	Goat fat
7	Enanthic acid	Heptanoic acid	CH₃(CH₂)₅COOH
8	Caprylic acid	Octanoic acid	CH₃(CH₂)₆COOH	Coconuts and breast milk
9	Pelargonic acid	Nonanoic acid	CH₃(CH₂)₇COOH	Pelargonium
10	Capric acid	Decanoic acid	CH₃(CH₂)₈COOH	Coconut and Palm kernel oil
11	Undecylic acid	Undecanoic acid	CH₃(CH₂)₉COOH
12	Lauric acid	Dodecanoic acid	CH₃(CH₂)₁₀COOH	Coconut oil and hand wash soaps
13	Tridecylic acid	Tridecanoic acid	CH₃(CH₂)₁₁COOH
14	Myristic acid	Tetradecanoic acid	CH₃(CH₂)₁₂COOH	Nutmeg
15	Pentadecanoic acid		CH₃(CH₂)₁₃COOH
16	Palmitic acid	Hexadecanoic acid	CH₃(CH₂)₁₄COOH	Palm oil
17	Margaric acid	Heptadecanoic acid	CH₃(CH₂)₁₅COOH
18	Stearic acid	Octadecanoic acid	CH₃(CH₂)₁₆COOH	Chocolate, waxes, soaps, and oils
19	Nonadecylic acid		CH₃(CH₂)₁₇COOH	Fats, vegetable oils, pheromone
20	Arachidic acid	Icosanoic acid	CH₃(CH₂)₁₈COOH	Peanut oil

Other carboxylic acids
Compound class	Members
unsaturated monocarboxylic acids	acrylic acid (2-propenoic acid) – CH₂=CHCOOH, used in polymer synthesis
Fatty acids	medium to long-chain saturated and unsaturated monocarboxylic acids, with even number of carbons examples docosahexaenoic acid and eicosapentaenoic acid (nutritional supplements)
Amino acids	the building-blocks of proteins
Keto acids	acids of biochemical significance that contain a ketone group, e.g. acetoacetic acid and pyruvic acid
Aromatic carboxylic acids	benzoic acid, the sodium salt of benzoic acid is used as a food preservative, salicylic acid – a beta hydroxy type found in many skin-care products, phenyl alkanoic acids the class of compounds where a phenyl group is attached to a carboxylic acid.
Dicarboxylic acids	containing two carboxyl groups examples adipic acid the monomer used to produce nylon and aldaric acid – a family of sugar acids
Tricarboxylic acids	containing three carboxyl groups example citric acid – found in citrus fruits and isocitric acid
Alpha hydroxy acids	containing a hydroxy group example glyceric acid, glycolic acid and lactic acid (2-hydroxypropanoic acid) – found in sour milk tartaric acid – found in wine
Divinylether fatty acids	containing a doubly unsaturated carbon chain attached via an ether bond to a fatty acid, found in some plants

Carboxyl radical

The radical ^•COOH (CAS# 2564-86-5) has only a separate fleeting existence.^[3] The acid dissociation constant of ^•COOH has been measured using electron paramagnetic resonance spectroscopy.^[4] The carboxyl group tends to dimerise to form oxalic acid.

Physical properties

Solubility

Carboxylic acid dimers

Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (the carbonyl –C=O) and hydrogen-bond donors (the hydroxyl –OH), they also participate in hydrogen bonding. Together the hydroxyl and carbonyl group forms the functional group carboxyl. Carboxylic acids usually exist as dimeric pairs in nonpolar media due to their tendency to “self-associate.” Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas higher carboxylic acids are less soluble due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be rather soluble in less-polar solvents such as ethers and alcohols.^[5]

Boiling points

Carboxylic acids tend to have higher boiling points than water, not only because of their increased surface area, but because of their tendency to form stabilised dimers. Carboxylic acids tend to evaporate or boil as these dimers. For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporised, both of which increase the enthalpy of vaporization requirements significantly.

Acidity

Carboxylic acids are Brønsted–Lowry acids because they are proton (H⁺) donors. They are the most common type of organic acid.

Carboxylic acids are typically weak acids, meaning that they only partially dissociate into H⁺ cations and RCOO⁻ anions in neutral aqueous solution. For example, at room temperature, in a 1-molar solution of acetic acid, only 0.4% of the acid molecules are dissociated. Electronegative substituents give stronger acids.

Carboxylic acid^[6]	pK_a
Formic acid (HCOOH)	3.75
Acetic acid (CH₃COOH)	4.76
Chloroacetic acid (CH₂ClCO₂H)	2.86
Dichloroacetic acid (CHCl₂CO₂H)	1.29
Trichloroacetic acid (CCl₃CO₂H)	0.65
Trifluoroacetic acid (CF₃CO₂H)	0.23
Oxalic acid (HO₂CCO₂H)	1.27
Benzoic acid (C₆H₅CO₂H)	4.2

Deprotonation of carboxylic acids gives carboxylate anions; these are resonance stabilized, because the negative charge is delocalized over the two oxygen atoms, increasing the stability of the anion. Each of the carbon–oxygen bonds in the carboxylate anion has a partial double-bond character.

Odour

Carboxylic acids often have strong odors, especially the volatile derivatives. Most common are acetic acid (vinegar) and butyric acid (human vomit). Conversely esters of carboxylic acids tend to have pleasant odors and many are used in perfume.

Characterization

Carboxylic acids are readily identified as such by infrared spectroscopy. They exhibit a sharp band associated with vibration of the C–O vibration bond (ν_C=O) between 1680 and 1725 cm⁻¹. A characteristic ν_O–H band appears as a broad peak in the 2500 to 3000 cm⁻¹ region.^[5] By ¹H NMR spectrometry, the hydroxyl hydrogen appears in the 10–13 ppm region, although it is often either broadened or not observed owing to exchange with traces of water.

Occurrence and applications

Many carboxylic acids are produced industrially on a large scale. They are also pervasive in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins.

Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers).

Synthesis

Industrial routes

In general, industrial routes to carboxylic acids differ from those used on smaller scale because they require specialized equipment.

Oxidation of aldehydes with air using cobalt and manganese catalysts. The required aldehydes are readily obtained from alkenes by hydroformylation.
Oxidation of hydrocarbons using air. For simple alkanes, the method is nonselective but too inexpensive to be useful. Allylic and benzylic compounds undergo more selective oxidations. Alkyl groups on a benzene ring oxidized to the carboxylic acid, regardless of its chain length. Benzoic acid from toluene, terephthalic acid from para-xylene, and phthalic acid from ortho-xylene are illustrative large-scale conversions. Acrylic acid is generated from propene.^[7]
Base-catalyzed dehydrogenation of alcohols.
Carbonylation is versatile method when coupled to the addition of water. This method is effective for alkenes that generate secondary and tertiary carbocations, e.g. isobutylene to pivalic acid. In the Koch reaction, the addition of water and carbon monoxide to alkenes is catalyzed by strong acids. Acetic acid and formic acid are produced by the carbonylation of methanol, conducted with iodide and alkoxide promoters, respectively, and often with high pressures of carbon monoxide, usually involving additional hydrolytic steps. Hydrocarboxylations involve the simultaneous addition of water and CO. Such reactions are sometimes called "Reppe chemistry":

HCCH + CO + H₂O → CH₂=CHCO₂H

Some long-chain carboxylic acids are obtained by the hydrolysis of triglycerides obtained from plant or animal oils; these methods are related to soap making.
fermentation of ethanol is used in the production of vinegar.

Laboratory methods

Preparative methods for small scale reactions for research or for production of fine chemicals often employ expensive consumable reagents.

oxidation of primary alcohols or aldehydes with strong oxidants such as potassium dichromate, Jones reagent, potassium permanganate, or sodium chlorite. The method is amenable to laboratory conditions compared to the industrial use of air, which is "greener", since it yields less inorganic side products such as chromium or manganese oxides.
Oxidative cleavage of olefins by ozonolysis, potassium permanganate, or potassium dichromate.
Carboxylic acids can also be obtained by the hydrolysis of nitriles, esters, or amides, in general with acid- or base-catalysis.
Carbonation of a Grignard and organolithium reagents:

RLi + CO₂ → RCO₂Li

RCO₂Li + HCl → RCO₂H + LiCl

Halogenation followed by hydrolysis of methyl ketones in the haloform reaction
The Kolbe–Schmitt reaction provides a route to salicylic acid, precursor to aspirin.

Less-common reactions

Many reactions afford carboxylic acids but are used only in specific cases or are mainly of academic interest:

Disproportionation of an aldehyde in the Cannizzaro reaction
Rearrangement of diketones in the benzilic acid rearrangement involving the generation of benzoic acids are the von Richter reaction from nitrobenzenes and the Kolbe–Schmitt reaction from phenols.

Reactions

Carboxylic acid organic reactions

The most widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (–OH) group is replaced with a metal cation. Thus, acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate, carbon dioxide, and water:

CH₃COOH + NaHCO₃ → CH₃COO⁻Na⁺ + CO₂ + H₂O

Carboxylic acids also react with alcohols to give esters. This process is heavily used in the production of polyesters. Likewise, carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a major biochemical process that requires ATP.

The hydroxyl group on carboxylic acids may be replaced with a chlorine atom using thionyl chloride to give acyl chlorides. In nature, carboxylic acids are converted to thioesters.

Carboxylic acid can be reduced to the alcohol by hydrogenation or using stoichiometric hydride reducing agents such as lithium aluminium hydride.

N,N-Dimethyl(chloromethylene)ammonium chloride (ClHC=N⁺(CH₃)₂Cl⁻) is a highly chemoselective agent for carboxylic acid reduction. It selectively activate the carboxylic acid and is known to tolerate active functionalities such as ketone as well as the moderate ester, olefin, nitrile, and halide moieties.^[8]

Specialized reactions

As with all carbonyl compounds, the protons on the α-carbon are labile due to keto–enol tautomerization. Thus, the α-carbon is easily halogenated in the Hell–Volhard–Zelinsky halogenation.
The Schmidt reaction converts carboxylic acids to amines.
Carboxylic acids are decarboxylated in the Hunsdiecker reaction.
The Dakin–West reaction converts an amino acid to the corresponding amino ketone.
In the Barbier–Wieland degradation, an carboxylic acid on an aliphatic chain having a simple the methylene bridge at the alpha position can have the chain shortened by one carbon. The inverse procedure is the Arndt–Eistert synthesis, where an acid is converted into acyl halide, which is then reacted with diazomethane to give one additional methylene in the aliphatic chain.
Many acids undergo oxidative decarboxylation. Enzymes that catalyze these reactions are known as carboxylases (EC 6.4.1) and decarboxylases (EC 4.1.1).
Carboxylic acids are reduced to aldehydes via the ester and DIBAL, via the acid chloride in the Rosenmund reduction and via the thioester in the Fukuyama reduction.
In ketonic decarboxylation carboxylic acids are converted to ketones.
The Kolbe electrolysis is an electrolytic, decarboxylative dimerization reaction. In other words, it gets rid of the carboxyl groups of two acid molecules, and joins the remaining fragments together.

References

^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "carboxylic acids".
^ Recommendations 1979. Organic Chemistry IUPAC Nomenclature. Rules C-4 Carboxylic Acids and Their Derivatives.
^ Milligan, D. E.; Jacox, M. E. (1971). "Infrared Spectrum and Structure of Intermediates in Reaction of OH with CO". Journal of Chemical Physics. 54 (3): 927–942. Bibcode:1971JChPh..54..927M. doi:10.1063/1.1675022.
^ The value is pK_a = −0.2 ± 0.1. Jeevarajan, A. S.; Carmichael, I.; Fessenden, R. W. (1990). "ESR Measurement of the pK_a of Carboxyl Radical and Ab Initio Calculation of the Carbon-13 Hyperfine Constant". Journal of Physical Chemistry. 94 (4): 1372–1376. doi:10.1021/j100367a033.
^ ^a ^b Morrison, R.T.; Boyd, R.N. (1992). Organic Chemistry (6th ed.). ISBN 0-13-643669-2.
^ Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. pp. 5–94 to 5–98. ISBN 1439855110.
^ Riemenschneider, Wilhelm (2002). "Carboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_235. .
^ Fujisawa, Tamotsu; Sato, Toshio. "Reduction of carboxylic acids to aldehydes: 6-Ooxdecanal". Org. Synth. 66: 121. doi:10.15227/orgsyn.066.0121. ; Coll. Vol., 8, p. 498

External links

Carboxylic acids pH and titration – freeware for calculations, data analysis, simulation, and distribution diagram generation

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 月経前症候群および月経前不快気分障害の疫学および病因 epidemiology and pathogenesis of premenstrual syndrome and premenstrual dysphoric disorder
2. 慢性的な手の湿疹 chronic hand eczema
3. エストロゲン関連片頭痛 estrogen associated migraine
4. Atopic dermatitis (eczema): Pathogenesis, clinical manifestations, and diagnosis

English Journal

Ultrasound-assisted surface treatment of ZrO2 with BSA and incorporating in PVC to improve the properties of the obtained nanocomposites: Fabrication and characterization.

Mallakpour S1, Hajjari Z2.
Ultrasonics sonochemistry.Ultrason Sonochem.2018 Mar;41:350-360. doi: 10.1016/j.ultsonch.2017.09.041. Epub 2017 Sep 23.
PMID 29137761

Conducting electrospun fibres with polyanionic grafts as highly selective, label-free, electrochemical biosensor with a low detection limit for non-Hodgkin lymphoma gene.

Kerr-Phillips TE1, Aydemir N1, Chan EWC1, Barker D1, Malmstro M J2, Plesse C3, Travas-Sejdic J4.
Biosensors & bioelectronics.Biosens Bioelectron.2018 Feb 15;100:549-555. doi: 10.1016/j.bios.2017.09.042. Epub 2017 Sep 28.
PMID 29017070

Effects of storage and yogurt matrix on the stability of tocotrienols encapsulated in chitosan-alginate microcapsules.

Tan PY1, Tan TB1, Chang HW1, Tey BT2, Chan ES2, Lai OM3, Baharin BS1, Nehdi IA4, Tan CP5.
Food chemistry.Food Chem.2018 Feb 15;241:79-85. doi: 10.1016/j.foodchem.2017.08.075. Epub 2017 Aug 24.
PMID 28958562

Japanese Journal

Role of the Tyr270 residue in 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase from Mesorhizobium loti

Journal of bioscience and bioengineering 123(2), 154-162, 2017-02
NAID 40021112404

Surface ionic charge dependence on the molecular mobility and self-assembly behavior of ionomers produced from carboxylic acid-terminated dendrimers

Polymer journal 49(2), 245-254, 2017-02
NAID 40021079008

Accuracy and Validity of AREC (Alkoxy Radical Elimination Capacity) Assay in Evaluating the Antioxidant Abilities of Various Biosubstances

Bulletin of the Chemical Society of Japan 90(2), 223-230, 2017
NAID 130005332360

「カルボン酸」

　　[★]

英: carboxylic acid